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Old 06-18-2006, 07:40 AM
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big block chevy piston to wall clearance question

Hi everybody,

I have a 468 CI, in that block, it was hyper speed pro piston, I just bough forged piston from ebay, Speed pro part number L2349-F60. My question is:

What will be the best piston to wall clearance if I want to used around a 175 or 200 hp nitrous. Some people said max 5 thousand and other one said 7 thousand..

If I have to honed all the cylinder, I dont want to miss my shot and I want everything to be perfect.

I will used total seal piston ring with the proper gap for the nitrous...

I need the more advice as possible...plz help me....

Thanks in advance, Stephane

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Old 06-18-2006, 08:03 AM
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Sounds like a good question for "Tom" (Oops... or "BOB")


I have a question though...? Using nitrous then what is your max target RPM...?

Last edited by Bumpstick; 06-20-2006 at 08:23 PM.
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Old 06-18-2006, 08:09 AM
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I used to build engines.that don't mean nothing everyone does things a little different,i wouldbe good with .0045''-.0055'' .make sure you measure the piston correctly and that you use an accurate bore gauge.also are the pistons nurld?
if the piston has a short skirt it's considerd a race piston and you don't want to have no .007'' clearance you'll end up with piston slap causing a cracked skirt.
good luck!
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Old 06-18-2006, 10:41 AM
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Quote:
Originally Posted by Bumpstick
Sounds like a good question for "Tom"


I have a question though...? Using nitrous then what is your max target RPM...?
On my cam, the max rpm is 6800 rpm...but my problem is: I have a magnum car with 575 lift both sides and 305 duration on both sides. I know a nitrous cam prefer to have more duration on exaust, but I do with what I have...

Stephane
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Old 06-18-2006, 10:44 AM
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Quote:
Originally Posted by nitro_baller4692
I used to build engines.that don't mean nothing everyone does things a little different,i wouldbe good with .0045''-.0055'' .make sure you measure the piston correctly and that you use an accurate bore gauge.also are the pistons nurld?
if the piston has a short skirt it's considerd a race piston and you don't want to have no .007'' clearance you'll end up with piston slap causing a cracked skirt.
good luck!
Sorry Nitro baller, I dont understant this question : ''also are the pistons nurld?''

can you explain to me plz..

Stephane
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Old 06-18-2006, 02:25 PM
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Quote:
Originally Posted by Ratoflic
On my cam, the max rpm is 6800 rpm...but my problem is: I have a magnum car with 575 lift both sides and 305 duration on both sides. I know a nitrous cam prefer to have more duration on exaust, but I do with what I have...

Stephane

are you using Oval port or retangle port heads? what intake? Valve size? any portwork? header size?


2wld4u
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Old 06-18-2006, 05:48 PM
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Quote:
Originally Posted by 2wld4u
are you using Oval port or retangle port heads? what intake? Valve size? any portwork? header size?


2wld4u
Oval port head, full ported and polish, severy duty manley 2.19 and 1.88 valves....Headers Hooker competition 2 inch primary and 3.5 collector

Do you need more information ??
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Old 06-18-2006, 06:06 PM
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Quote:
Originally Posted by Ratoflic
Oval port head, full ported and polish, severy duty manley 2.19 and 1.88 valves....Headers Hooker competition 2 inch primary and 3.5 collector

Do you need more information ??

sounds like a stout build, not crazy about the cam, but you can upgrade later, the only differance is I use 2.25 intake valves.. If your portwork is up to par it will pull hard to 6500, the weiand stealth intake is plenty with mild portwork..

2wld4u
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Old 06-18-2006, 06:59 PM
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If memory serves me, the 2349 piston is the replacement LS6 piston. The recommended clearance is .004. An extra .001 to .0015 should be sufficient given the rpm you are planning on running. I know people who have run .007-.0075 with that piston on strip only applications. At that clearance they do tend to rock in the bore quite a bit though.
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Old 06-18-2006, 07:05 PM
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Quote:
Originally Posted by 2wld4u
sounds like a stout build, not crazy about the cam, but you can upgrade later, the only differance is I use 2.25 intake valves.. If your portwork is up to par it will pull hard to 6500, the weiand stealth intake is plenty with mild portwork..

2wld4u
My intake is a Weiand TEam G intake, ported match to the porting of the head. It a high rise intake with a 750 mighty demon distributor and a Davis unified ignition distributor matchet to the engine.
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Old 06-18-2006, 07:30 PM
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Back to original question... Each piston manufacturer has a spec for wall clearance. Depending on use/material and skirt type. Contact the manufacturer or a knowledgable dealer. I think the term you are looking for is Knurled. This expands the skirt a slight amount. Leaves a pattern on piston skirt.
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Old 06-18-2006, 11:46 PM
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piston clearance

Make sure what piston that you have .Some pistons called power forged or forged are not forged alu. but a mixture or materials and are probably hiperputectic and carry close wall clearances,under 0025.What you also need to check closely is your piston ring gap.The gap needs to be opened up with the use of the juice or you will snatch the tops off of your pistons.i WOULD THINK THAT YOU WOULD GO WITH AROUND 018 TO 020,RING GAP BUT YOU NEED TO CHECK FOR YOUR PERSONAL APPLICATION.Good luck
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Old 06-19-2006, 12:51 PM
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Quote:
Originally Posted by Ratoflic
My intake is a Weiand TEam G intake, ported match to the porting of the head. It a high rise intake with a 750 mighty demon distributor and a Davis unified ignition distributor matchet to the engine.

thats a good intake as well, and considering your going to be spraying, the single plane might help with distribution problems, I equalize the ports when I port them, some intake designs even with good portwork on the heads makes for tuning problems, just keep this in mind when your spraying...



2wld4u
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Old 06-19-2006, 01:20 PM
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Quote:
Originally Posted by BOBCRMAN@aol.com
Back to original question... Each piston manufacturer has a spec for wall clearance. Depending on use/material and skirt type. Contact the manufacturer or a knowledgable dealer. I think the term you are looking for is Knurled. This expands the skirt a slight amount. Leaves a pattern on piston skirt.
I agree...
Check with the piston mfr for correct specs. Part Number Lookup says recommended clearance for this piston is 0.0040

IMO, Speed-Pro / TRW is a good name brand with a solid reputation.

I have read that forged pistons tend to "grow" more than hyperutes when they warm up. ALWAYS get the engine up to operating temp before revving it up or driving it hard.

The benefit of forged is that they withstand detonation better than hyperutes ... great for nitrous/blower applications.
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Old 06-19-2006, 01:59 PM
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Quote:
Originally Posted by 66GMC
I agree...
Check with the piston mfr for correct specs. Part Number Lookup says recommended clearance for this piston is 0.0040

IMO, Speed-Pro / TRW is a good name brand with a solid reputation.

I have read that forged pistons tend to "grow" more than hyperutes when they warm up. ALWAYS get the engine up to operating temp before revving it up or driving it hard.

The benefit of forged is that they withstand detonation better than hyperutes ... great for nitrous/blower applications.
So, thats mean, if they recommend 40 thousand, I have to add 10 or 15 thousand for the heavy load of nitrous for a total of 50 or 55 thousand??



Stephane
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Last edited by Ratoflic; 06-19-2006 at 02:11 PM.
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